Effect of rate of weight gain and EPD of the sire on puberty of crossbreed heifers (Angus x Nellore) weaned early

Author(s)

José Paulo Roman Barroso

• Document type: Master's Dissertation
• Press: Pirassununga.
• Institution: Universidade de São Paulo (USP). Faculdade de Medicina Veterinária e Zootecnia (FMVZ/SBD)
• Defense date: 2019-01-11

Examining board members

Alexandre Vaz Pires; Marcos Vinicius de Castro Ferraz Junior; Evandro Maia Ferreira

• Advisor: Alexandre Vaz Pires

Abstract

The puberty in beef heifers is a limiting factor for the increase of productivity, being influenced by several factors. The aim of this study was to evaluate the rate of weight gain from three to seven months of age and the EPD of the bull on puberty of beef heifers. Sixty F1 heifers (Angus x Nellore) weaned early (102 ± 4.3 days; 103 ± 4.7 kg) were used in an experiment arranged in a 2x2 factorial scheme. Factor 1 was the Rate of Gain in period 1 (3 to 7 months of age) in which heifers were submitted to High ADG, with DMI ad libitum (HG; ADG estimated at 1000 g / animal / day, n = 30 heifers ) or submitted to Medium ADG, with DMI of 1.5% of body weight (MG; GMD estimated at 700 g / animal / day, n = 30 heifers). In period 2 (from the 7th month of age until puberty), all heifers received the ad libitum diet. Factor 2 was the EPD for scrotal circumference (SC) of the sire: Positive EPD (PE) of the precocious sires and Negative EPD (NE) of the non-precocious sires. ADG, DMI and FE were measured at the end of each period; weight at seven months; age, weight and BCS at puberty; rate of puberty and serum concentrations of IGF-1 and insulin at months 3, 5, 7, 10 and 12. Statistical analysis were performed by SAS 9.3. There was interaction between factors only for CMS in period 1 (P = 0.02). Considering the Rate of Gain, HG heifers showed higher DMI (P <0.0001) and ADG (P <0.0001) in period 1 in relation to MG heifers. Consequently, the weight at seven months was also higher (P = 0.002). In period 2, MG heifers presented higher ADG (P = 0.05) than HG heifers. Considering the EPD, heifers of PE presented higher DMI (P = 0.03) and ADG (P = 0.07) in period 2, in relation to NE heifers. The PE heifers were heavier at seven months (P = 0.02) and at puberty (P = 0.0005). The puberty rate at 15 months was higher for PE heifers (P = 0.03). There was no reduction in the age at puberty of Angus x Nellore heifers by the difference in the Rate of Gain from 3 to 7 months. The EPD for SC of precocious bulls increased the puberty rate of Angus x Nellore heifers at 15 months of age. (AU)

• FAPESP's process: 16/14019-3 - Effect of metabolic imprinting and EPD for sexual precocity on puberty in crossbreed (Angus X Nellore) heifers weaned early
• Grantee: José Paulo Roman Barroso
• Support Opportunities: Scholarships in Brazil - Master